After winning each of the previous two National League pennants and thoroughly dominating the senior circuit in 1902 by posting a record of 103-36, the Pittsburgh Pirates captured their third straight league championship by finishing the regular season 6 ½ games ahead of the second-place New York Giants, with a record of 91-49. Having spent the previous few years shifting back and forth between the outfield, first base, third base, and shortstop, Pittsburgh great Honus Wagner became the team’s full-time shortstop for the first time. In addition to displaying surprising dexterity in the field, the powerfully-built Wagner had another outstanding year at the plate, leading the National League with a .355 batting average and 19 triples, finishing second with 101 runs batted in, and placing among the league leaders in several other offensive categories. Meanwhile, teammates Ginger Beaumont and Fred Clarke also excelled for the Pirates. Beaumont led the league with 137 runs scored and 209 hits, while Clarke finished second to Wagner in batting, with a mark of .351, and led the league with a .532 slugging percentage.
The second-place Giants had the league’s top two pitchers in “Iron Man” Joe McGinnity and Christy Mathewson. McGinnity led all N.L. hurlers with 31 wins, 434 innings pitched, 44 complete games, and 55 appearances, while pitching to a 2.43 earned run average. Mathewson finished 30-13, with a 2.26 ERA, 366 innings pitched, 37 complete games, and a league-leading 267 strikeouts.
Other outstanding performers and notable events around the league included:
• The Cubs' Frank Chance stole 67 bases, a record for first basemen.
• Part of Philadelphia’s Baker Bowl collapsed, killing 12 fans.
• The Pirates shut out their opposition for a record 57 consecutive innings.
• Joe McGinnity pitched and won two doubleheaders in an eight-day period. He also won a third twin-bill during the month. His 434 innings pitched remain the National League record.
• The Chicago Cubs acquired future Hall of Fame pitcher Mordecai "Three Finger" Brown from the St. Louis Cardinals.
• Philadelphia’s Chick Fraser tossed a no-hitter against Chicago on Sept. 18.
• Cincinnati shortstop Tommy Corcoran accumulated a record 14 assists in a game on August 7.
• Pittsburgh's Sam Leever led the National League with a 2.06 ERA and seven shutouts.
• Boston’s Pat Moran made 214 assists, a record for catchers.
Additionally, late in the 1903 season, the owners of the two first-place clubs agreed amongst themselves to play a best-of-nine postseason world championship series. The American League's Boston Americans came back to win 5-3 after being down 3-1 to the heavily favored Pirates. The star of the series was Pittsburgh's Deacon Phillippe, who pitched an incredible five complete games, going 3-2 with a 2.86 ERA. The success of the series led to the formal World Series, which started in 1905 and has continued until today.
- 1903 World Series, Baker Bowl, Chick Fraser, Christy Mathewson, Deacon Phillippe, Frank Chance, Fred Clarke, Ginger Beaumont, Honus Wagner, Joe McGinnity, John McGraw, Mordecai Brown, New York Giants, Pat Moran, Pittsburgh Pirates, Sam Leever, Tommy Corcoran